Apparatus for evaluating quenching media



y 1960 E. J. TQTON EIAL 2,937,335

. APPARATUS FOR EVALUATING QUENCHING MEDIA Filed Jan. 28, 1958 INVENTORS cdV/azeJYZ/n d git Z3115 fizzaw/'z ATTORAE'Y APPARATUS FOR EVALUATING QUENCHING MEDIA Edward J. Toton, Birmingham, and Anthony S. Strzelewicz, Detroit, Mich., assignors to General Motors Corperation, Detroit, Mich, a corporation of Delaware Application January 28, 1958, Serial No. 711,745

6 Claims. (Cl. '324-34) This invention relates to testing apparatus and more panticularly to an arrangement for evaluating the heat transfer capacity of materials. A particular field of application is the evaluation of quenching media used in metallurgical heat treatment processes in which the rate of temperature change is a significant factor.

This invention is based upon the behavior of metals described by Curies law that the permeability of paramagnetic substances is inversely proportional to the absolute temperature up to the Curie point. At the Curie point, the substances cease to have a permeability in excess of unity and become non-magnetic. The Curie point of a given metal specimen may be utilized as a convenient reference temperature in the evaluation of quenching media since the occurrence of this known temperature is signified by the change in magnetic properties. A method and apparatus based upon this principle is described and claimed in the copending application Serial No. 711,485, filed January 27, 1958 by Edward A. Bender for Method of Evaluating Quenching Media," and assigned to the assignee of the present invention.

In accordance with this invention, an automatic timer is provided to measure the elapsed time required for a particular quenching medium to change the temperature of a specimen having a known Curie point from a predetermined value to its Curie point. This is accomplished by a control circuit which is responsive to the entry of the specimen into the quenching medium and to the occurrence of the Curie point for starting and stopping the timer. More particularly, a movable support member is disposed within the quenching medium and is adapted to receive the specimen at an elevated temperature. Specimen sensing means such as a photosensit-ive element influences the control circuit to start the timer when the specimen enters the medium. Magnetic means adjacent the support member are effective to cause displacement thereof by magnetic linkage with the specimen upon the occurrence of the Curie point in its temperature change. Circuit means responsive to this displacement influence the control circuit to stop the timer. Thus the elapsed time for a predetermined temperature change is measured.

A more complete understanding of this invention may be had from the detailed description which follows taken with the accompanying drawing in which the single figure is a schematic diagram of the apparatus.

Referring now to the drawing there is shown an illustrative embodiment of the invention in testing apparatus for measuring the elapsed time required for a particular quenching fluid to change the temperature of a specimen from a predetermined value to its Curie point. In general, the apparatus comprises a receptacle 10 of electrically conductive material which contains a liquid quenching medium to be evaluated. The receptacle 10 is disposed upon a support plate 12 and accommodates a movable support member or cage 14 which is mounted "for pivotal motion about the support shaft 16. The

cage 14 is open at its top and is adapted to receive the United States Patent C metal specimen 18, suitably a spherical element of nickel, which has a known Curie point of 665 F. and which may be heated to 1625 F. just prior to immersion in the quenching liquid. The elapsed time required to cool the specimen from its predetermined high temperature to its Curie point is measured by the timer 20. The timer is provided with a control circuit including the timer relay circuit 22 which in turn is controlled by the timer starting circuit 24 and the timer stopping circuit 26. The control circuit is energized through the manual switches 28a and 28b which are mechanically coupled for concurrent actuation.

The timer starting circuit 24 responds to the introduction of the specimen into the quenching liquid to start the timer 20. This circuit, energized from alternating voltage source represented by conductors 30, extends through the manual switch 28a with its movable contact in either the on" position or test position to energize a pair of supply voltage conductors 32 and 34 which are connected across a rectifying circuit including the current limiting resistor 36, a filter condenser 38 and a diode rectifier 40. The direct voltage thus developed is applied across a photosensitive element 42 through the energizing coil of a relay 44 having a condenser 46 in parallel therewith to prevent relay chatter. The photosensitive element 42 is suitably a photoconductive device of the broad-area cell type which exhibits a change of resistance in'response to incident radiation. The photosensitive element 42 is disposed adjacent the receptacle 10 to respond to the radiation from the specimen 13 which emanates therefrom at its elevated temperature during its travel into the support cage 14. When the resistance of the photosensitive element is decreased momentarily by such radiation, the energizing winding of relay 44 is energized and its relay contacts 44a, in a circuit to be described presently, are actuated. Until the specimen enters the receptacle 10, however, the winding of relay 44 remains effectively deenergized.

To start the timer 20 in response to the entry of the specimen in to the receptacle 10, the timer relay circuit 22 is provided. This circuit is energized from the conductors 30 through the switch 28a and the interposed transformer 48. The timer relay circuit is connected across the secondary winding of the transformer 48 and includes the normally closed relay contacts 44a of relay 44, the winding of relay 5% and the normally open contacts 50a of relay 50. Switch 2811 is connected in parallel with the normally open relay contacts 50a and in its on position completes a circuit for energizing the winding of relay 50. This in turn closes the normally open contacts 50a to establish a holding circuit for maintaining the relay 50 energized, so long as the normally closed contacts 44a remain closed, even though switch 231) is further displaced to its test position. The relay 5G is adapted to actuate a set of timer contacts 50b for controlling the timer 20.

The timer 20 is energized from the conductors 30 when the switch 28a is in either its on or test positions and includes a constant speed motor 52 connected across the conductors 32 and 34 through the conductors 54 and 56. The motor 52 is mechanically coupled through a suitable gear train and a magnetic clutch 58 to an elapsed time indicator 60. The magnetic clutch 58 is connected across the conductors 54 and 56 through the normally closed relay contacts 50b of relay 50. Thus when the relay 50 is energized, the relay contacts 50b are open and the indicator 60 is stopped. However, upon entry of the specimen into the receptacle 10 and the ensuing momentary energization of relay 44, the relay 50 is de energized and the indicator 60 is started.

In order to stop the timer upon the occurrence of the Curie point of the specimen 18, the timer stopping circuit 26 is provided. This circuit extends across the relay contacts 50a from one terminal thereof and includes conductor 62 connected with the conductive support plate 12 which is conductively connected with the metallic receptacle 10. The pivoted cage 14 is also electrically conductive and is connected through conductor 64 to the other terminal of relay contacts 50a. A magnet 66, disposed adjacent the receptacle 10, has a magnetic field linking the specimen in its position within the cage 14. Thus when the specimen is at a temperature above its Curie point and is non-magnetic in character, the pivoted cage assumes its normal position, as indicated. However, upon the occurrence of the Curie point, the specimen 18 becomes magnetic in character and is attracted toward magnet 66 causing engagement of the cage 14 and receptacle it Thus the relay contacts 50a are shortcircuited and an energizing circuit for the relay 50 is completed causing the contacts 50a to be closed and the contacts 50b to be opened to stop the time indicator 60.

in operation, for conducting a test on the quenching liquid in receptacle 10, the manual switches 28a and 28b are displaced from the off position through the on position to the test position. If desired, the switch may be allowed to dwell at the on position to test the photosensitive element by employing radiation from an external source. The time indicator 60 can be started and stopped merely by turning the external radiating source on or off without resorting to the engagement of the cage 14 and receptacle 10. In this condition, the timer starting circuit, including the photosensitive element 42 is energized and the timer relay circuit 22, including the coil of relay 50, is de-energized as the normally closed relay contacts 44:: are opened while the photosensitive element 42 is energized. Since relay 50 is deenergized, its relay contacts 50b are closed to energize the magnetic clutch 58 causing the time indicator 60 to run. When the external energizing source is removed from the photosensitive element 42, the timer starting circuit is deenergized and the timer relay circuit 22 is energized through the normally closed relay contacts 44a, the coil of relay 50 and the switch 28b. Since relay 50 is energized, its relay contacts 56b are opened to deenergize the magnetic clutch 58 to prevent the time indicator 60 from running. When the switches 28a and 2812 are further displaced to the test position, the timer starting circuit 24 remains energized and the timer relay circuit 22 remains energized through the holding contacts 50a of relay 50. Accordingly, with relay S energized the timer contacts 50b remain open and the time indicator 60 is stopped.

In the performance of the test, the specimen 18 is heated to its predetermined temperature above the Curie point and dropped into the cage 14. Radiation from the specimen during its motion past the photosensitive element 42 causes a momentary decrease in the resistance of the element and hence the relay 44 is momentarily energized. This causes the relay contacts 44a to open momentarily to deenergize the relay 50. Consequently, the timer contacts 50b are closed and the clutch 58 is energized to start the time indicator 60 running. At the same time, the dcenergization of relay 50 causes its holding contacts 50a to open. Following the momentary energization of relay 44, the relay contacts 440. reclose but the relay 50 remains dcenergized because the holding contacts 59a have been opened. The time indicator 60 thus continues to run until the occurrence of the Curie point in the temperature change of specimen 18. At this point, the specimen becomes magnetic and is attracted toward the permanent magnet 66 causing engagement of the cage 14 with the receptaclewhich completes a short-circuit around the holding contacts 50a. Accordingly, the relay 50 is energized causing the timer contacts 50b to open and deenergize the clutch 58, thus stopping the time indicator 60. This completes the test and the measurement of elapsed time is recorded by the time indicator 60.

Although the description of this invention has been given with respect to a particular embodiment, it is not to be construed in a limiting sense. Numerous variations and modifications within the spirit and scope of the invention will now occur to those skilled in the art. For a definition of the invention, reference is made to the appended claims.

We claim:

1. Apparatus for measuring the time required to change the temperature of a metal specimen from a predetermined value to its Curie point, said apparatus comprising a movable support member adapted to receive said specimen, a timer including a control circuit for starting and stopping the timer, specimen sensing means adjacent the support member and connected with the control circuit for starting the timer upon entry of the specimen into the member, magnetic means adjacent the support member adapted to cause displacement of the member by a change of magnetic linkage with said specimen upon the occurrence of the Curie point in its temperature change, and circuit means responsive to displacement of the support member and connected with the control circuit for stopping the timer.

2. Apparatus for measuring the time required to change the temperature of a metal specimen from a predetermined value to its Curie point, said apparatus comprising a movable support member adapted to receive said specimen, a timer including a control circuit for starting and stopping the timer, a photosensitive element adjacent the support member and connected with the control circuit for starting the timer upon entry of the specimen into the member, a magnet adjacent the support member adapted 'to attract said specimen and displace said member upon the occurrence of the Curie point in its temperature change, and circuit means responsive to displacement of the member and connected with the control circuit for stopping the timer.

3. Apparatus for measuring the time required to change the temperature of a metal specimen from a predetermined value to its Curie point, said apparatus comprising a conductive receptacle for containing a quenching medium, a pivotally mounted conductive support member disposed within the receptacle and adapted to receive said specimen, a timer including a control circuit for starting and stopping the timer, a photosensitive element adjacent the support member and connected with the control circuit for starting the timer upon entry of the specimen into the member, a magnet adjacent the support member adapted to attract said specimen and displace said member into engagement with said receptacle upon the occurrence of the Curie point in the temperature change of said specimen, and circuit means including the member and the receptacle and connected with the control circuit for stopping the timer.

4. Apparatus for measuring the time required to change the temperature of a metal specimen from a predetermined value to its Curie point, said apparatus comprising a conductive receptacle for containing a quenching medium, a pivotally mounted conductive support member disposed Within the receptacle and adapted to receive said specimen, a timer including an elapsed time indicator, timer control contacts adapted to start and stop said indicator, a timer relay circuit including a relay for actuating said control contacts, a timer starting circuit including a photosensitive element adjacent the support member and adapted to control energization of the relay circuit, a magnet adjacent the support member adapted to attract said specimen and displace said member into engagement with said receptacle upon the occurrence of the Curie point in the temperature change of said specimen, and a timer stopping circuit including the support member and the receptacle and connected with the relay circuit to control energization thereof.

5. Apparatus for measuring the time required to change the temperature of a metal specimen from a predetermined value to its Curie point, said apparatus comprising a conductive receptacle for containing a quenching medium, a pivotally mounted conductive support member disposed within the receptacle and adapted to receive said specimen, a timer including a motor connected with an elapsed time indicator through a magnetic clutch, timer control contacts connected in circuit with said clutch, a timer relay circuit including a relay for actuating said control contacts, a timer starting circuit including a photosensitive element adjacent the support member and adapted to control the energization of the relay circuit, a magnet-adjacent the support member adapted to attract said specimen and displace said member into engagement with said receptacle upon the occurrence of the Curie point in the temperature change of said specimen, and a timer stopping circuit including the support member and the receptacle and connected with the relay circuit to control the energization thereof.

6. Apparatus for measuring the time required to change the temperature of a metal specimen from a predetermined value to its Curie point, said apparatus comprising a conductive receptacle for containing a quenching medium, a pivotally mounted conductive support member disposed within the receptacle and adapted to receive said specimen, a timer including a motor connected with an elapsed time indicator through a magnetic clutch, normally closed timer control contacts connected in circuit with said clutch, a timer relay circuit including a con trol relay for actuating said control contacts, normally open holding contacts and normally closed starting contacts; a timer starting circuit including a photosensitive element adjacent the support member and including a starting relay for actuating the starting contacts to deener-gize the relay circuit when the starting circuit is energized in response to radiation incident upon the photosensitive element from the specimen, a magnet adjacent the support member adapted to attract said specimen and displace said member into engagement with said receptacle upon the occurrence of the Currie point in the temperature change of said specimen, and a timer stopping circuit including the support member and the receptacle and connected across said holding contacts for energizing said relay circuit to open said control contacts and stop said timer.

References Cited in the file of this patent UNITED STATES PATENTS 1,778,655 Wyman Oct. 14, 1930 2,717,515 Pesante Sept. 13, 1955 2,730,894 Husa Jan. 17, 1956 

